Peroxy acid bleaching systems



United States Patent Ofice 3,384,596 Patented May 21, 1968 3,384,596PEROXY ACID BLEACHlN-G SYSTEMS John R. Moyer, Midland, Mich, assignor toThe Dow Chemical Company, Midland, Mich, a corporation of Delaware NoDrawing. Filed Dec. 30, 1965, Ser. No. 517,787 2 Claims. (Cl. 252--187)ABSTRACT OF THE DISCLOSURE The present invention relates to an aqueousbleaching composition which comprises an organic peroxy acid, a watersoluble source of an alkaline earth metal ion, and water, saidcomposition having a peroxy acid concentration which provides an activeoxygen concentration of from about to 150 parts per million.

This invention relates to bleaching and more particularly concerns animprovement in organic peroxy acid bleaching compositions and a methodof their use in bleaching operations whereby an unexpected increase inbleaching activity of organic peroxy acids is realized.

A primary object of the invention is to provide a novel system forincreasing the activity of peroxy acid-containing, or, peroxyacid-producing compositions, and particularly for increasing thebleaching activity thereof.

Another object of the invention is to optimize the bleaching activity oforganic peroxy acids thereby obtaining in bleaching operationsbrightness increases heretofore unrealized with peroxy acids alone. Arelated object is to provide a bleaching system and aqueous compositionwhich does not detrimentally aifect articles bleached therein.

Other objects and advantages will become apparent from the followingdetailed description of the invention:

The novel aqueous bleaching composition of the present inventioncomprises an organic peroxy acid selected from the group consisting ofmetachloroperoxy-benzoic acid, monoperoxyphthalic acid, or peroxyaceticacid, a water soluble source of an alkaline earth metal ion selectedfrom the group consisting of magnesium or calcium, and water, saidaqueous bleaching composition having an alkaline pH and a peroxy acidconcentration which provides an active oxygen concentration of fromabout 10 to 150 parts per million (p.p.m.). The aqueous bleachingcomposition is further characterized in that withmetachloroperoxybenzoic acid either calcium or magnesium ion is employedat a metal ion/peroxy acid ratio of from about 0.5 to about 1, withmonoperoxyphthalic acid magnesium ion is employed at a metal ion/peroxyacid ratio of from about 0.5 to about 2.5 and, with peroxyacetic acidcalcium ion is employed at a metal ion/peroxy acid ratio of from about0.5 to about 1.

The metal ion-to-peroxy acid ratio as used herein is based on moles ofsaid metal ion to each acid group in the peroxy acid selected.

The improvement in activity of the peroxy acid is in general in a directrelationship to the amount of said metal ion present in the solution.Greater concentration of said metal ions, though not detrimental to thearticle bleached, is of diminishing value in enhancing the activity ofthe selected peroxy acid.

in general, the present novel process for increasing the activity ofperoxy acids in aqueous solution and especially the bleaching activityof certain organic peroxy acid materials utilizing the improvedcomposition of the present invention comprises: providing an aqueousalkaline solution of metachloroperoxybenzoic acid, monoperoxyphthalicacid, or peroxyacetic acid, and introducing thereinto a water solublesource of an alkaline earth metal ion selected from the group consistingof magnesium or calcium, said aqueous alkaline solution having anapparent pH ordinarily of about 9 and preferably about 10, and a peroxyacid concentration expressed as active oxygen of from about 10 to about150 p.p.m., said aqueous alkaline bleaching solution containing saidmetal ion being characterized in that when metachloroperoxybenzoic acidis selected either calcium or magnesium ion is introduced therein in ametal ion-to-peroxy acid ratio of from about 0.5 to about 1, whenmonoperoxyphthalic acid is selected magnesium ion is introduced'thereinin an ion-to-peroxy acid ratio of from about 0.5 to about 2.5, and whenperoxyacetic acid is selected calcium ion is introduced therein in acalcium ion-to-peroxy acid ratio of from about 0.5 to about 1.

The calcium or magnesium ions are normally introduced into the peroxyacid solution as soluble inorganic salts.

In bleaching utilizing the novel aqueous composition of the presentinvention, a temperature within the range of from about F. to about 150F. is ordinarily employed, but a temperature range generally limitedonly by said 100 F. as a minimum temperature and the boiling point ofthe respective bleaching solution may operably be employed. Preferably atemperature within the range of from about to about F. is used duringbleaching.

The brightness increase obtained is directly related to the activeoxygen concentration, i.e., greater increases are obtained at the higheractive oxygen concentrations. Generally an active oxygen concentrationof from about 10 to about 150 p.p.m. is employed in bleaching withperoxy acids, preferably from about 50 to about 100 p.p.m.

It is noteworthy that all metal ions and, in fact, even all alkalineearth metal ions do not operate to activate or increase the bleachingpotential of the aforesaid peroxy acids. For example, the transitionmetal ions, iron, nickel, copper, mercury and cobalt actually serve todecrease the brightness of articles bleached by peroxy acids. Similarly,the alkali metal ions or the alkaline earth metal ions other thancalcium and magnesium are not operable to any significant extent in thepresent invention.

The presence of the calcium or magnesium metal ions in the indicatedratio with the peroxy acid in the solution unexpectedly and verysignificantly enhances and increases the bleaching activity of theparticular peroxy acid specified providing a powerful oxidizingsolution, thereby obtaining unusually high brightness increases infabric articles bleached therein.

The amount of water employed in the composition is that amount necessaryto provide the aforesaid concentration of active oxygen in the solution.The pH of the bleaching solutions of the present invention are adjustedto an alkaline pH by eg the addition of caustic, etc.

The present invention distinguishes from methods concerning thestabilization of bleaching compositions. For example, though magnesiumsulfate in bleach baths containing hydrogen peroxide serves to stabilizesaid baths by e.g., minimizing decomposition, neither calcium normagnesium ions enhance the bleaching activity of hydrogenperoxide-containing solutions. In addition, as is shown in the followingexamples, neither magnesium nor calcium ion is effective to increase thebleaching activity of all peroxy acids, contrary to what might beexpected if the ion were acting or being employed as a stabilizer.

The following examples serve to further illustrate the present inventionbut are not to be construed as limiting the invention thereto.

For purposes of the following examples and in order to make relativequantitative brightness determinations, a brightness (reflectance) valueof zero (0) was assigned 3 1.0 a piece of unbleached muslin which hadbeen washed in a 2.0 gram solution of a hOusehold detergent called Tide.All brightness readings in the following examples were obtained using aHunter Photovolt Reflectometer with a green tri-stimulus lilter.

Example I Five by five (5 x 5") inch squares of unbleached muslin(brightness of were bleached in a solution at l30 F. and pH of 9.8containing 2 grams of Tide detergent and 0.254 gram of 85% puremetachloroperoxybenzoic acid, corresponding to 20 parts per million(p.p.m.) active oxygen. The reflectance of the muslin bleached in themetachloroperoxybenzoie acid was determined to be 65.

Two identical solutions to that above were prepared. Calcium nitrate(Ca(NO -4H O) was added to one and magnesium sulfate (MgSO -4H O) to theother in a molar amount equal to that of the meiaehloroperoxybenzoicacid. Unbleached muslin squares were then exposed to each solution at130 F. for about 10 minutes, rinsed, dried and then tested forbrightness. Brightness increases of 11 and 6 points respectively on thescale defined above, were obtained over the brightness of muslinbleached in the detergent-metachloroperoxybenzoic acid solution notcontaining said calcium or magnesium values.

Example 11 Four bleaching baths were prepared. Each contained one literof tap water and 2.0 grams of Tide detergent. Three contained sufficientmetachloroperoxybenzoic acid to give 50 ppm. active oxygen. To one ofthese three baths, no additional chemicals were added. To a second wasadded a solution of magnesium sulfate sufficient to give one mole ofmagnesium ion per acid group in the metachloroperoxybenzoic acid. To thethird bath was added a solution of calcium nitrate, in the same molarproportion with the peroxy acid. Each bath was maintained at 130 F. andadjusted to pH 9.8 by addition of NaOH solution.

A inch square of unbleached cotton muslin was agitated in each bath forminutes and then rinsed and dried. The reflectance of the cloth wasmeasured with the Hunter Photovolt Refiectometer. The reflectance of theunbleached muslin was set at zero and that of the muslin bleached in 50ppm. active oxygen as metachloroperoxybenzoic acid alone was establishedat 39. The bleaching results obtained by introduction of the aforesaidcalcium and magnesium ions are given in Table I below.

From the figures in Table I it can be seen that the present inventionprovides outstanding brightness increases over the brightness obtainedwith metachloropcroxybenzoic acid alone.

Example III The tests set forth in Example II were repeated but at atemperature of 100 F. The increase in brightness (reflectance) obtainedis presented in Table II below:

Example IV Similarly as in Example I unbleached muslin squares werebleached in a solution containing 2.0 grams of Tide detergent and anequal molar mixture of sodium perborate and phthalic anhydride (whichreact in aqueous solution to form monoperoxyphthalic acid) for about 10minutes at F. The solution was adjusted to a pH of 9.8 and containedabout 50 ppm. active oxygen. The brightness obtained was 20 asdetermined on the scale wherein the brightness of unbleached muslin wasabout 0.

To an identical solution was added 2 moles of per mole of the phthalicanhydride and like squares of unbleached muslin were contacted with thesolution for 10 minutes at 130 F. A total brightness measurement of 30points was obtained, representing a significant brightness increase of10 points over that obtained with the monoperoxyphthalic acid solutioncontaining no magnesium sulfate.

Example V The effect of increasing amounts of MgSO -7H O in bleachingunbleached muslin squares with m-chloroperoxybenzoic acid to give anactive oxygen concentration of 50 ppm. was determined in a series ofexperiments at 130 F. in which the moles of magnesium ion (introduced asMgSO per acid group in the metachloroperoxybenzoic acid was varied. Theresults of these tests are given in Table III below:

TABLE III Molar Ratio of Mg++ ion-to-aeid group Total 7 Total UainBrightness 0 (control) 1 .2 73 77 Example VI The effect of increasingamounts of MgSO -7H O in treating unbleached muslin squares withmonoperoxyphthalic acid was determined in a series of experiments inwhich the moles of the Mg++ io-n, introduced as MgSO to the acid groupsin the acid was varied. The test conditions of temperature, time and pHare those of the Example IV. The results are given in Table IV below.

TABLE IV Molar ratio: Total brightness 0 (control) 20 0.25 (control) 18Table IV shows that with respect to monoperoxyphthalic acid, increasesin brightness are obtained by increasing the moles of Mg ion to the acidat least to about 2.5, whereas at a ratio of less than about, e.g., 0.25no increase in brightness is provided over that obtained with the monoperoxyphthalic acid alone.

Example VII Squares of unbleached muslin fabric (brightness at 0) werebleached for minutes in a bleaching solution comprising 2.0 grams ofTide detergent in one liter of tap water at a temperature of 130 F. Tothis was added sufiicient peroxyacetic acid to give 100 p.p.m. activeoxygen and aqueous sodium hydroxide to adjust the pH to 10. Thebrightness of the muslin obtained from bleaching in this manner was 45.

Two identical bleaching baths were prepared. To one was added a solutionof calcium nitrate in a mole quantity equal to the number of acid groupsin the peroxyacetic acid. To the other bath, as a comparative or controlexample was added a similar amount of magnesium sulfate.

The brightness of the muslin after bleaching in the calciumnitrate-containing solution was about 58, whereas, the brightness of themuslin after bleaching in the magnesium sulfate-containing solution wasabout 46, this being substantially the same as for the peroxyacetic acidalone.

This example illustrates the outstanding increases in brightnessobtained by the introduction of calcium ion to peroxyacetic acid, whileessentially no bleaching improvement is obtained by the introduction ofmagnesium ion to peroxyacetic acid.

Similarly as in the foregoing examples, other combinations andconcentrations of metal ions and peroxyacids maybe employed in solutionto optimize or increase the activity over that of the peroxyacid alone.

The present novel invention may be modified and changed withoutdeparting from the spirit or scope thereof, and it is understood theinvention is only limited as defined in the appended claims.

I claim:

1. An aqueous bleaching composition consisting essentially of an organicperoxy acid selected from the group consisting ofmetachloroperoxybenzoic acid, monoperoxyphthalic acid, or peroxyaceticacid, a water soluble salt of an alkaline earth metal ion selected fromthe group consisting of magnesium or calcium, and water, said aqueousbleaching composition having an alkaline pH and a peroxy acidconcentration which provides an active oxygen concentration of fromabout 10 to 150 parts per million, said aqueous bleaching compositionbeing further characterized in that with metachloroperoxybenzoic acid analkaline earth metal ion selected from the group consisting of magnesiumor calcium is employed at a metal ion to peroxy acid ratio of from about0.5 to about 1.0, with monoperoxyphthalic acid magnesium ion is employedat a metal ion to peroxy acid ratio of from about 0.5 to about 2.5, andwith peroxyacetic acid calcium ion is employed at a metal ion to peroxyacid ratio of from about 0.5 to about 1.

2. The aqueous bleaching composition of claim 1 wherein said compositionhas a pH of at least about 9.

References Cited UNITED STATES PATENTS 2,254,434 9/1941 Lind et al 252 X3,075,921 1/1963 Brecklehurst et al. 252186 X 3,156,654 11/1964 Konecny252-186 X LEON D. ROSDOL, Primary Examiner.

I. GLUCK, Assistant Examiner.

